U.S. Pat. No. 4,754,012 to Yoldas discloses a multicomponent composition comprising an organoalkoxysilane with a combination of other components such as hydrolyzable alkoxides of aluminum, titanium, tantalum and hafnium to form an inorganic oxide polymer network providing abrasion resistance and also optimizing other properties such as alkali resistance, adhesive strength, chemical resistance, water stability and index of refraction for optical coatings.
Optical quality abrasion resistant coated plastic materials generally require a coating that protects the substrate from the damaging effects of ultraviolet (UV) radiation. Protection from ultraviolet radiation is especially important for polycarbonate, since hydrolytic degradation is apparently accelerated by UV exposure. Conventional UV stabilizers do not impart sufficient protective capacity to abrasion resistant coatings, as sufficient amounts of most typical organic UV absorbers cannot be added to water/alcohol based sol-gel type abrasion resistant coating compositions due to limited solubility and further without adversely affecting hardness and adhesion of the coating. Moreover, typical UV absorbers may gradually become deactivated after prolonged exposure, and also may gradually be leached from the composition.